PWM Pulse Help

I’m trying to design a computer program that will use the digital outputs of a computer’s parallel port to control a jaguar through PWM. From what I know already, one pin goes to ground, but what are the other two pins on the PWM cable used for?

Also, how would I calculate the pulse on/off time to sending high/low values through the PWM pulse pin to set the Jaguar to certain speeds (I.e. what would I need to send through the 3 pins to get the equivalent of half speed on the jaguar output)?


The red or center wire is unused by a Jaguar.
The white wire is for the signal pulses.

white wire= signal

[strike]red=power[/strike] NOT USED. read previous posts.


Internal to the Jaguar, the white wire (which contains the PWM signal) is put through the diode of an opto isolator and the current returns via the black wire. As pointed out, the red wire isn’t used. The other side of the opto isolator goes to a GPIO pin of the microcontroller in the Jaguar which measures the pulse width.

You can get the Jaguar’s schematics which might provide you more insight and help with your interfacing exercise… The CD accompanying the developer’s version of Jaguar are available for free download on the TI web site. See

Also be aware of the pulse width and frequency requirements. By default, the Jaguar uses a wider pulse width range than standard hobby servos or the Victor. NI and TI (then Luminary Micro) worked together to provide more granularity to the output and therefore the PWM width is wider. It can also be operated with a period in the range of 5-30 ms (5 ms for a 200 Hz update rate). If you need it to work in the same range as a standard hobby servo, you’ll need to calibrate the Jaguar, and remember to recalibrate it if you put it back on an FRC robot later.